During periods of high humidity and warm weather, fungal molds can begin to develop on sorghum heads. White and cream- colored sorghums are more vulnerable because there is less tannic acid in the seed coat. Tannic acid is a natural fungicide.
While losses are generally less than 5%, it is not unheard of to reach levels of 30% or more depending on the hybrid, time of flowering, maturity and soil type. Grain molds can affect both the quantity and quality of the grain. Unlike corn however, there are few reports of problems with mycotoxins developing in the grain that could lead to livestock feeding problems.
A number of different fungi can be responsible for grain mold including Alternaria, Fusarium, Colletotrichum, and Curvularia. In Kansas, grain molds generally are black to gray to green-black in color (see photo). The velvety growth can partially or entirely cover the berry. Berries damaged by head feeding worms or birds are more likely to be colonized by mold.
Grain from fields with significant levels of head mold should only be stored for very short periods of time since the problem can worsen in storage bins and lead to heating and crusting problems. If moldy grain must be placed in a bin, grain temperature should be lowered to below 50 F as soon as practical. Grain moisture should be below 13.5% and relative humidity in the bin should be kept below 50%.
Figure 1. Head mold in grain sorghum. Photo courtesy of Doug Jardine, K-State Research and Extension.